Adapter for holding a sample container to facilitate sensing of liquid level in the sample container

ABSTRACT

An adapter for holding a sample container includes a main body portion and a tapered body portion that forms a continuation of the main body portion. The tapered body portion includes a mouth opening that is of lesser diameter than the diameter of the main body portion. The mouth opening of the adapter is sized to provide direct support of a sample container which holds a liquid sample. During liquid level sensing ultrasonic waves from an ultrasound detector are reflected back to the sound detector as echoes from the lip flange of the sample container and from the liquid level within the sample container. The tapered surface of the adapter deflects sound echoes away from the sound detector. The adapter is thus invisible to the ultrasound detector. The echo from the liquid level is a variable duration echo and the echo from the lip flange of the sample container is a fixed duration echo that is always of lesser duration than the variable duration echo. Thus the sound detector can easily recognize the liquid level echo and convert the characteristics of the liquid level echo to a discernible liquid level.

BACKGROUND OF THE INVENTION

[0001] This invention relates to automatic sensing of liquid level in asample container, and more particularly to a novel adapter for holding asample container to facilitate liquid level sensing, and a novel methodof sensing liquid level in a sample container.

[0002] Ultrasonic liquid level sensing is often used in automatic sampleanalysis systems of the type disclosed in U.S. Pat. Nos. 5,268,167 and5,399,497. During automated sample analysis a liquid sample, such asblood serum, is subjected to a variety of tests. The serum sample, whichis used as a source material for the tests, is usually placed in arelatively small container of fixed diameter, such as a Microtainer®tube, since the desired tests can be performed with relatively smallamounts of diluted sample. For each discrete test on the serum aselected amount of diluted sample is aspirated from the sample containerand combined with a predetermined amount of reagent to produce achemical reaction that corresponds to a distinctive test on the sample.

[0003] The sample tests provide chemical information relating todifferent characteristics of the blood to assist in determining thehealth or well being of the individual being tested.

[0004] The quantity of sample which is used in each reagent test must beprecisely controlled because test interpretation is based on anexpectation that a predetermined amount of sample is combined with apredetermined amount of reagent. One known way of ensuring that thereagent tests are based on selected amounts of sample and reagent is tomeasure the sample level in a sample container before and after eachaspiration of sample and to perform corresponding measurements on thereagent in a reagent container.

[0005] The liquid level measurement information will confirm that theintended amount of sample has in fact been used in a specific test. Thusconsecutive measurements of sample level in a sample container provideconfirmation that the required amount of liquid is removed from thesample container for each test. The sample level measurements for eachtest also provide an ongoing determination of the amount of liquid thatremains in the sample container.

[0006] In known sample analysis systems of the type previously referredto it is common practice to transport one or more sample containers todifferent locations in the sample analysis system. Sample containers areusually transported in sample tube racks that carry larger diametertubes than the Microtainer® tube, such as Vacutainer® tubes which haveother uses in the sample analysis system. The sample tube rackpreferably maintains tubes of all sizes in an upright position since thetubes are often in an open condition.

[0007] In order to simultaneously transport relatively small samplecontainers, such as Microtainer® tubes with other larger diameter tubes,each Microtainer® tube is usually supported in a larger diameter tube .However, because of a great disparity in size between the Microtainer(ttube and the Vacutainer® tube it is necessary to cradle the Microtainer®tube in an intermediate holding device such as an Easi-nest® holder.

[0008] The Easi-nest® holder, which is open at one end and closed at theopposite end, has a tapered inside surface that is sized to bear againstthe Microtainerg tube when the Microtainer® tube is pushed into theEasi-nest® holder. The Easi-nest® holder also has a flange at the mouthportion that is large enough to rest on the mouth portion of theVacutainer® tube. The support of a Microtainer® tube in an Easi-nest®holder held in a Vacutainer® tube is referred to herein as a sample tubesupport system or a Microtainerg tube support system.

[0009] The sensing of liquid level in the Microtainer® tube can beaccomplished while the Microtainer® tube is supported in an Easi-nest®holder and elevated in a Vacutainer® tube held in a test tube rack orsample tube rack.

[0010] One known method of sensing liquid level is to employ anultrasound detector. The ultrasound detector is located at apredetermined elevation over the travel path of the sample tube rackthat holds the Microtainer® tube support system.

[0011] During liquid level sensing the ultrasound detector emits anultrasonic wave directed against a horizontal surface of theMicrotainer® tube support system that is proximate the liquid level. Theultrasonic wave is reflected as a sound echo from the horizontal surfaceback to the ultrasound detector. The characteristics of the echo areinterpreted in a known manner by the ultrasound detector to indicate thedistance between the ultrasound detector and the surface that reflectedor produced the echo.

[0012] If the echo producing surface is in fact the liquid level in theMicrotainer® tube than the distance between the liquid surface and theultrasound detector can be determined by measuring the duration of timebetween the emission of the ultrasound wave and the receipt of the echofrom the liquid level.

[0013] However, when a sample rack includes a Microtainer® tubesupported in an Easi-nest® holder and a Vacutainer® tube it is difficultto selectively direct an ultrasonic wave against only the liquid levelin the Microtainer® tube. To deal with this problem an ultrasonic waveis periodically emitted as the sample rack passes under the ultrasounddetector. Ultrasonic waves are thus sequentially directed against otherhorizontal surfaces of the Microtainer® tube support system in additionto the liquid level. These horizontal surfaces include the mouth portionof the Microtainer® tube and the mouth portion of the Easi-nest® holder.

[0014] Based on a known height of the mouth portion of the Microtainer®tube from a reference level we can determine a first distance betweenthe ultrasound detector and the mouth portion of the Microtainer® tube.Also based on a known height of the mouth portion of the Easi-nest®holder from the reference level we can determine a second distancebetween the ultrasound detector and the mouth portion of the Easi-nest®holder. Thus the mouth portion surfaces of the Microtainer® tube and theEasi-nest® holder can be identified from their corresponding echoes. Theremaining echo would thus be associated with the liquid level in theMicrotainer® tube.

[0015] Generally the liquid level 110 in a Microtainer® tube 20 isinitially at a higher level than the mouth portion 140 of the Easi-nest®holder 132 (see FIGS. 10 and 11). However, as liquid 80 is depleted fromthe Microtainer® tube 20 the liquid level 110 recedes toward the mouthlevel 140 of the Easi-nest® holder 132. When liquid level 110 in theMicrotainer® tube 20 closely approaches the level of the mouth portion140 of the Easi-nest® holder 132 it becomes difficult to distinguishbetween the echo from the liquid level 110 in the Microtainer® tube 20and the echo from the mouth portion 140 of the Easi-nest® holder 132.Thus there is a range of liquid level 110 in the Microtainer® tube 20that can be confused with the level of the mouth portion 140 of theEasinest® holder 132 which can lead to errors in liquid level sensing.

[0016] It is thus desirable to provide a sample tube support structurefor a sample container such as a Microtainert® tube that facilitatesdistinguishing a liquid level surface echo from an echo produced by astructural surface of the Microtainer® tube support system.

[0017] Another problem in measuring liquid level in a Microtainer® tubesupported in an Easi-nest® holder is that the amount by which aMicrotainer® tube projects from an Easi-nest® holder may vary due tomanufacturing tolerances. Inconsistent positioning of the Microtainer®tube in the Easi-nest® holder is also common because the Microtainer®tube is usually manually pushed into snug engagement with the taperedsurface of the Easi-nest® holder and there is no fixed stop position forthe Microtainer® tube in the Easi-nest(g) holder. It is thus desirableto provide a Microtainer® tube support system wherein the Microtainer®tube is always located in the same position in the support system.

OBJECTS AND SUMMARY OF THE INVENTION

[0018] Among the several objects of the invention may be noted theprovision of a novel support system or adapter for holding a sample tubecontainer or Microtainer® tube in a sample rack to facilitate liquidlevel sensing in the sample container, a novel adapter for holding asample container to facilitate liquid level sensing in the samplecontainer by an ultrasound detector, a novel adapter having a reduceddiameter mouth portion to provide direct support for a sample container,a novel adapter for direct support of a sample container without anintermediate support device between the sample container and theadapter, a novel adapter that directly supports a sample container at alip flange of the sample container, a novel adapter having a bodystructure that diverts ultrasound wave echoes away from the ultrasounddetector, a novel adapter having a body portion with a tapered sectionto divert ultrasonic wave echoes away from the ultrasound detector, anovel adapter that holds a sample container and is substantiallyinvisible to an ultrasound detector to enable the ultrasound detector toreceive only the sound echoes from the lip flange of the samplecontainer and from the liquid level in the sample container and notreceive echoes from any other structure of the sample tube supportsystem, and a novel method of ultrasonically sensing liquid level in asample container.

[0019] Other objects and features of the invention will be in partapparent and in part pointed out hereinafter.

[0020] In accordance with the invention an adapter for holding a samplecontainer is a generally tubular structure having a main body portionand a tapered body portion. The main body portion preferably has a fixeddiameter. The tapered body portion extends from the main body portion toa mouth opening that is of lesser diameter than the main body portion.The tapered body portion has an outer diameter that increases inmagnitude in a direction from the mouth opening toward the main bodyportion.

[0021] The mouth opening of the adapter is sized to receive a relativelysmall diameter sample container such that a lip portion or lip flange ofthe sample container rests upon the mouth opening of the adapter. Thetapered body portion of the adapter includes inner surface projectionsthat bear slightly against the sample container when it is received inthe mouth opening of the adapter.

[0022] In some embodiments of the invention the adapter is formed as atwo piece structure with one component being the tapered body portionand the other component being the main body portion.

[0023] In another embodiment of the invention the adapter has anenlarged bottom opening. The adapter can thus be formed as a one pieceintegral structure.

[0024] In one embodiment of the invention the main body portion and thetapered body portion are joined together at a snap fit joint. The snapfit joint includes a first lip that projects radially outwardly of theone of the main body portion and the tapered body portion and a secondlip that projects radially inwardly of the other of the main bodyportion and the tapered body portion. Thus the main body portion and thetapered body portion can bypass each other with slight interference topermit one the lips to bypass the other lip to form an inseparable snapfit joint between the main body portion and the tapered body portion.

[0025] In a further embodiment of the invention the main body portionand the tapered body portion are joined together at complementary shapedstep portions formed at the joint.

[0026] In some embodiments of the invention the bottom portion of theadapter has a curved semi-spherical shape.

[0027] In several embodiments of the invention the tapered body portionof the adapter has two distinct tapered sections. One of the two taperedsections has a lesser amount of slope than the other tapered section.Preferably the tapered section with the lesser amount of slope includesthe mouth opening of the adapter.

[0028] When a sample container is provided with serum and placed in theadapter the entire body portion of the sample container is received inthe adapter. Thus only the lip flange of the sample container rests uponthe mouth opening of the adapter.

[0029] The main body portion of the adapter can be of the same diameteras that of a standard size test tube and placed in a sample tube rackwith other test tubes of standard diameter. The rack can be transportedbelow an ultrasound detector for purposes of liquid level sensing. Theultrasound detector emits sound waves that are reflected back to thedetector as echoes from only the mouth portion of the sample containerand the liquid level within the sample container.

[0030] Any ultrasonic waves that reach the tapered body portion of theadapter are reflected away from the sound detector. Therefore, the sounddetector does not receive any echoes from the adapter and consequentlydoes not recognize any surfaces of the adapter. The adapter is thusessentially invisible to the ultrasound detector.

[0031] Since the lip flange of the sample container is always at thesame position in the adapter the sound detector can always recognize thelip flange of the sample container based on the echo it produces. Theonly other echo received by the sound detector is from the liquid levelsurface which is always below the lip flange of the sample container.Therefore the sound detector can clearly distinguish between the echofrom the liquid level surface and the echo from the lip flange of thesample container. The sound detector can also clearly distinguish anyechoes from the sample rack, which are substantially weaker than theechoes from the sample container and the liquid level.

[0032] Since no other echoes from the adapter or the sample containerare received by the sound detector the adapter provides a reliable meansfor facilitating the sensing of liquid level in the sample container.

[0033] The invention accordingly comprises the constructions and methodshereinafter described, the scope of the invention being indicated in theclaims.

DESCRIPTION OF THE DRAWINGS

[0034] In the drawings,

[0035]FIG. 1 is a simplified perspective view an adapter incorporatingone embodiment of the invention, the adapter supporting a samplecontainer and being shown exploded from a sample tube rack with testtubes and other similar adapters;

[0036]FIG. 2 is an elevational view thereof on a sample rack partlyshown in section and positioned below an ultrasonic sound detector;

[0037]FIG. 3 is a simplified elevational view thereof in sequence withother sample racks being transported below the ultrasound detector;

[0038]FIG. 4 is an enlarged perspective view thereof;

[0039]FIG. 5. is a sectional view thereof taken on line 5-5 of FIG. 4;

[0040]FIG. 6 is a sectional view thereof taken on line 6-6 of FIG. 5;

[0041]FIG. 7 is an exploded view thereof;

[0042]FIG. 8 is an enlarged exploded sectional view thereof without thesample container;

[0043]FIG. 9 is an enlarged schematic elevational view thereof partlyshown in section during ultrasound liquid level sensing;

[0044]FIGS. 10 and 11 are elevational views, partly shown in section, ofa prior art sample container support system during ultrasound liquidlevel sensing;

[0045]FIG. 12 is a simplified perspective view of another embodimentthereof;

[0046]FIG. 13 is an enlarged sectional view thereof;

[0047]FIG. 14 is an exploded view thereof,

[0048]FIG. 15 is a sectional view thereof taken on the line 15-15 ofFIG. 12;

[0049]FIG. 16 is a sectional view thereof taken on the line 16-16 ofFIG. 15;

[0050]FIG. 17 is a sectional view of another embodiment thereof and;

[0051]FIG. 18 is a sectional view thereof taken on the line 18-18 ofFIG. 17.

[0052] Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0053] Referring to the drawings, especially FIGS. 1 and 4-8, an adapterincorporating one embodiment of the invention is generally indicated bythe reference number 10.

[0054] The adapter 10 is a generally tubular structure preferably formedof plastic, such as clear polystyrene. The adapter 10 includes a top endwith a mouth opening 12 defined by a lip portion 14 (FIG. 7) and abottom end with a closed hemi-spherical portion 16.

[0055] The mouth opening 12 of the adapter 10 is sized to accommodate arelatively small tubular sample container 20, such as a Microtainer®tube. The sample container 20 has a mouth opening 22 (FIG. 7) defined bya lip flange 24 and a closed bottom portion 26. The sample container 20also has a body portion 28 of fixed diameter that is accommodated in themouth opening 12 of the adapter 10 to permit the lip flange 24 of thesample container 20 to rest upon the lip portion 14 of the adapter 10 asshown in FIG. 5.

[0056] The adapter 10 has a main body portion 30 with a fixed diameterand a tapered body portion 36 that extends from the main body portion 36to the mouth opening 12. The tapered body portion 36 has an outer wall38 with a diameter that increases in a direction from the mouth opening12 toward the main body portion 30.

[0057] A joint 40 (FIG. 8) connects an upper end 46 of the main bodyportion 30 and a lower end 48 of the tapered body portion 36. The joint40 includes an annular lip 42 on the main body portion 30 that projectsradially outwardly from an annular recess 44 at the upper end 46 of themain body portion 30.

[0058] The joint 40 also includes an internal annular recess 50 (FIG. 8)formed at the lower end 48 of the tapered body portion 36. The annularrecess 50 defines an annular ledge surface 60. An annular lip portion 54spaced slightly below the annular ledge 60 projects radially inwardlyfrom the annular recess 50. The annular lip portion 54 includes agenerally horizontal upper surface 56 and an upwardly inclined lowersurface 58.

[0059] The annular lip portion 42 on the main body portion 30 and theannular lip portion 54 on the tapered body portion 36 are sized suchthat the lip portion 42 is movable against the inclined lower surface 56of the lip portion 54 with slight interference to bypass the lip portion54 and become locked in position between the horizontal upper surface 56and the ledge 60 of the annular recess 50 (FIG. 5).

[0060] The joint 40 connecting the tapered body portion 36 and the mainbody portion 30 is an inseparable snap fit joint.

[0061] The tapered body portion 36 preferably has two distinct taperedsections 70 and 72 (FIG. 8), with the tapered section 70 having a lesseramount of slope than the tapered section 72. Three equally spacedprojections 74 (FIG. 8) are formed on an inner surface 76 of the taperedbody portion 36 to project inwardly a predetermined amount from theinner surface 76. The projections 74 are preferably formed at a junction78 between the tapered sections 70 and 72. The projections 74 are sizedto make slight contact with the body portion 26 of the sample container20 when the sample container 20 is positioned in the adapter 10 as shownin FIG. 5. Thus the sample container 20, when inserted in the adapter10, is gently detented therein by engagement of the projections 74against the body portion 26 of the sample container 20. The force of theprojections 74 against the body portion 26 of the sample container 20 iseasily overcome to ensure that the lip flange 24 of the sample container20 can rest upon the lip portion 14 of the adapter 10.

[0062] In using the adapter 10 a sample container 20 containing serum 80that is to be subjected to sample analysis is supported in the adapter10 as shown in FIG. 9. The adapter 10 is supported in a sample rack 82(FIGS. 1 and 9) of the type shown in U.S. Des. Pat. No. 421,130. Therack 82 is adapted to be automatically transported in a sample analysissystem along a known transport device 84 (FIG. 3).

[0063] As shown in FIGS. 1-3 the rack 82 can hold a plurality ofadapters 10, with each adapter holding a sample container 20 with serum80. The serum 80 in each sample container 20 is usually taken from adifferent test subject or individual. The sample rack 82 can also holdstandard size test tubes 90 containing reagents, diluents, or othermaterials generally indicated by the reference number 92 that are usedat different locations in the sample analysis system and are transportedto such locations with the sample rack 82.

[0064] During sample analysis or testing of the serum 80 in a selectedsample container 20 a predetermined amount of serum is aspirated (notshown) for each test in a battery of tests that are to be performed. Ameasurement of liquid level 110 (FIG. 9) is made before and after eachaspiration of serum sample 80 to confirm that a requisite amount ofsample is aspirated and also to determine the amount of serum 80 thatremains in the sample container 20 after each aspiration.

[0065] Referring to FIG. 3 the liquid level measurement is performedusing a known ultrasound detector 100 that is positioned over thetransport device 84 that transports the sample racks 82. Beforeultrasound testing is carried out the ultrasound detector 100 isprovided with a series of input parameters. For example, the lip flange24 (FIG. 9) of the sample container 20 is always at a fixed height “L”from a selected reference level. The lip flange 24 is thus always at afixed distance “M” from the ultrasound detector 100 (FIG. 9).

[0066] Referring to FIG. 9 the liquid level 110 of the serum 80 in thesample container 20 is always below the level of the lip flange 24. Theliquid level 110 is thus always at a distance (N) from the ultrasounddetector 100 that is greater than the distance (M) between the detector100 and the lip flange 24 of the sample container 20.

[0067] The ultrasound detector 100 emits an ultrasonic wave directed,for example, at an adapter 10 that passes directly below the detector100. When an ultrasonic wave 102 hits the horizontal surface of the lipflange 24 an echo 104 is produced and reflected back to the ultrasounddetector 100. The ultrasound detector 100 can determine the distance ofthe echo producing surface (the lip flange 24) from the ultrasounddetector 100 based on the duration of time between emission of theultrasonic wave and reception of the echo 104.

[0068] Thus an echo 104 from the lip flange 24 of the sample container20 will always correspond to the distance M between the lip flange 24 ofthe sample container 24 and the detector 100.

[0069] When the ultrasound detector 100 produces a wave 108 (FIG. 9)that reaches the liquid level 110 in the sample container 20 an echo 112is reflected back to the detector 100. The echo 1 12 corresponds to thedistance “N” between the liquid level 1 10 and the sound detector 100.Since the distance “N” differs from and is greater than the distance “M”the sound detector will recognize the distance “N” as representingliquid level.

[0070] It should be noted that the echo 112 corresponding to thedistance “N” will always be within a known range of liquid levels. Thusthe sound detector 100 can reliably interpret the echo 112 ascorresponding to the distance “N” which represents liquid level.

[0071] Any ultrasonic waves from the ultrasound detector 100 that reachthe tapered surface 38 of the tapered body portion 36 will reflect awayfrom the sound detector 100. Thus the sound detector 100 will notreceive an echo from sound waves that hit the tapered surface 38.Therefore the tapered surface 38 of the adapter 10 is essentiallyinvisible to the ultrasound detector 100.

[0072] Under this arrangement the adapter 10 with the sample tube 20presents only two surfaces to the detector 100 that produce a detectableecho, namely the lip flange surface 24 of the sample container 20 andthe liquid level surface 110 within the sample container 20.Consequently the sound detector 100 can easily determine which of thetwo echoes 104 and 112 represent liquid level 110 and which echo doesnot represent liquid level, because the lip flange echo 104 is alwaysconstant and of lesser duration than the liquid level echo 112.

[0073] Significant problems in distinguishing liquid level are evidentfrom the prior art sample tube support system 130 shown in FIGS. 10 and11 wherein the sample containers 20 in FIGS. 10 and 11 each contain thesame amount of the serum 80.

[0074] Referring to FIGS. 10 and 11 the known sample tube support system130 includes a sample container 20, such as a Microtainer® tube,supported in an Easi-nest® holder 132 which in turn is supported in aVacutainer® tube 134. The Easi-nest® holder 132 includes a tapered innersurface 138 that bears against the body portion 26 of the samplecontainer 20, when the sample container 20 is accommodated in theEasi-nest® holder 132.

[0075] The height of Vacutainer® tubes 34 are substantially uniform. TheEasi-nest® holder 132 is of substantially uniform size and shape anddimension but the inside tapered surface 138 can deviate from a norm dueto manufacturing tolerances. The sample tube container 20 is ofsubstantially uniform dimensions. However, the amount by which samplecontainer 20 is recessed into the Easi-nest® holder 132 can varysignificantly (compare H and H′ in FIGS. 10 and 11) due to tolerances ofthe tapered surface 138 and inconsistencies in the manual force used topush the sample tube container 20 into the Easi-nest® holder 132.

[0076] The distance K (FIGS. 10 and 11) between lip flange 140 of theEasi-nest® holder 132 and the detector 100 is substantially constant dueto the uniform height of the Vacutainer® tube 134 and the uniformthickness of the lip flange 140 which rests on the mouth portion of theVacutainer® tube 134. However, the height H of the sample tube 20 from areference level in FIG. 10 differs from the reference level height H′ ofthe sample tube 20 in FIG. 11 to illustrate that there is no consistencyin the amount by which the sample tube 20 is pushed into the Easi-nest®holder 132. Thus the distance I between the sample tube lip flange 24and the detector 100 in FIG. 10 is less than the corresponding distanceI′ in FIG. 11. Consequently similar liquid levels 110 in FIGS. 10 and 11can have different distances J and J′ (FIGS. 10 and 11) from the sounddetector 100.

[0077] When the sound detector 100 receives an echo from the lip flange24 of the sample container 20 in FIG. 10 and FIG. 11 the echoes will notbe of the same duration because the lip flange 24 in FIG. 10 is at acloser distance (I) to the sound detector 100 than the lip flange 24 inFIG. 11 which is at a greater distance I′.

[0078] The sound detector 100 will also receive an echo from the liquidlevel surface 110 of the serum 80 in FIGS. 10 and 11. As serum 80 isdepleted from the sample container 20 the liquid level 110 will approachthe level of the lip flange 140 of the Easi-nest® holder 132. Thus therecan be confusion between an echo from the lip flange 140 of theEasi-nest® holder 132 and an echo from the liquid level 110. Theproblems in sensing liquid level in the prior art sample tube supportsystems 130 shown in FIGS. 10 and 11 are manifest because the systems130 present at least three horizontal surfaces that reflect echoes backto the sound detector 100, namely the lip flange 24 of the samplecontainer, the liquid level 110 and the lip flange 140 of the Easi-nest®holder. Since the echo produced by the liquid level 110 can be confusedwith the echo produced by the lip flange 140 of the Easi-nest® holderliquid level sensing in the prior art sample tube support system 130shown in FIGS. 10 and 11 is not reliable.

[0079] A sample tube adapter incorporating another embodiment of theinvention is generally indicated by the reference number 150 in FIG. 12.

[0080] The sample tube adapter 150 includes a main body portion 152 anda tapered body portion 154. An upper end of the main body portion 152and a lower end of the tapered body portion 154 include complementaryshaped step portions 156 and 158. An ultrasonic welding ridge 160 isprovided at one of the step portions such as the step portion 158. Themain body portion 152 and the tapered body portion 154 of the sampletube adapter 150 are connected by ultrasonic welding of the stepportions 156 and 158 in a known manner. The sample tube adapter 150 isotherwise structurally similar to the sample tube adapter 10 andsupports a sample container 20 in the same manner as the sample tubeadapter 10.

[0081] Still another embodiment of the sample tube adapter is generallyindicated by the reference number 170 in FIG. 17. The sample tubeadapter 170 is a one piece structure that includes a bottom opening 172,a tapered body portion 174 and a main body portion 176. The adapter 170is otherwise similar in structure to the adapter 10 or the adapter 150and supports a sample container 20 in the same manner as the sample tubeadapter 10.

[0082] Some advantages of the invention evident from the foregoingdescription include a sample tube adapter that supports a samplecontainer at a constant known elevation. The adapter and samplecontainer reflect back to an ultrasound detector only one echo from astructural surface, namely the lip flange of the sample container andonly one echo from the liquid level in the sample container that issupported by the adapter. Thus the ultrasound detector can reliablydistinguish liquid level from the lip flange since the echo from theliquid level is always of longer duration than the echo from the lipflange.

[0083] Another advantage of the invention is that the adapter has atapered surface that deflects any ultrasound waves that hit the taperedsurface away from the sound detector so that the sound detector does notdetect any echoes from the tapered surface portion of the adapter. Noother surface portions of the adapter reflect echoes back to theultrasound detector. The adapter is thus invisible to the ultrasounddetector. Still another advantage of the invention is that the adapterwill always support the sample container at a consistent known height.Another advantage of the adapter is that it directly supports the samplecontainer and eliminates the need for any intermediate support devicebetween the sample container and the adapter. A further advantage isthat the adapter provides a simple and novel method for liquid levelsensing, eliminates guess work and confusion and is thus more reliablethan known prior art methods for sensing liquid level in a samplecontainer.

[0084] In view of the above it will be seen that the several objects ofthe invention are achieved and other advantageous results attained. Asvarious changes can be made in the above constructions and methodswithout departing from the scope of the invention it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. An adapter for holding a sample container tofacilitate liquid level sensing in the sample container, said adaptercomprising, a) a generally tubular structure with a main body portionhaving a first outside diameter, b) a tapered body portion extendingfrom said main body portion and having a mouth opening for receiving andsupporting a sample container, the mouth opening having a second outsidediameter that is of lesser magnitude than the first outside diameter,and c) said tapered body portion having an outer diameter that increasesin magnitude in a direction from said mouth opening toward the main bodyportion.
 2. The adapter as claimed in claim 1 wherein said tapered bodyportion includes an inner surface with spaced projections projectingradially inwardly from the inner surface to bear against a samplecontainer of predetermined size received in said mouth opening of saidadapter.
 3. The adapter as claimed in claim 1 wherein the main bodyportion and the tapered body portion are formed as a one piece integralstructure.
 4. The adapter as claimed in claim 3 wherein said main bodyportion has bottom portion with a bottom opening.
 5. The adapter asclaimed in claim 4 wherein the body portion has a curved semi-sphericalshape and said bottom opening is at the lowermost portion of said curvedsemi-spherical shape.
 6. The adapter as claimed in claim 1 wherein saidmain body portion has a closed bottom portion.
 7. The adapter as claimedin claim 6 wherein said bottom portion has a curved semi-sphericalshape.
 8. The adapter as claimed in claim 1 wherein said main bodyportion and said tapered body portion are separately formed and joinedtogether such that said tapered body portion is a continuous extensionof said main body portion.
 9. The adapter as claimed in claim 8 whereinsaid main body portion and said tapered body portion are formed ofplastic and are joined together by ultrasonic welding.
 10. The adapteras claimed in claim 8 wherein said main body portion and said taperedbody portion are formed of plastic and connected together at a joint,one of said main body portion and said tapered body portion including afirst lip that projects radially outwardly and the other of said mainbody portion and said tapered body portion including a second lip thatprojects radially inwardly, said first and second lips being sized suchthat they can bypass each other with slight interference to permit oneof said lips to bypass the other said lip to form an inseparable snapfit joint between the main body portion and the tapered body portion.11. The adapter as claimed in claim 1 wherein the tapered body portionhas two distinct tapered sections, one of the tapered sections having alesser amount of slope than the other tapered section.
 12. The adapteras claimed in claim 11 wherein the tapered section with the lesseramount of slope includes the mouth opening.
 13. An adapter for holding asample container to facilitate liquid level sensing in the samplecontainer, said adapter comprising, a) a generally tubular structurehaving an open mouth portion at one end and a bottom portion at anopposite end, said tubular structure including a main body section and atapered body section extending from said main body section. b) saidtapered body section having the open mouth portion of said tubularstructure and a tapered wall portion that diverges from the open mouthportion to a maximum diameter where the tapered body section meets themain body section, and c) said main body section having an outsidediameter that does not exceed the maximum diameter of the tapered bodysection.
 14. The adapter as claimed in claim 13 wherein the tapered bodyportion has two distinct tapered sections, one of the tapered sectionshaving a lesser amount of slope than the other tapered section.
 15. Theadapter as claimed in claim 14 wherein the tapered section with thelesser amount of slope includes the mouth opening.
 16. The adapter asclaimed in claim 13 wherein the main body portion and the tapered bodyportion are formed as a one piece integral structure.
 17. The adapter asclaimed in claim 16 wherein said main body portion has bottom portionwith a bottom opening.
 18. The adapter as claimed in claim 13 whereinsaid main body portion and said tapered body portion are separatelyformed and joined together such that said tapered body portion is acontinuous extension of said main body portion.
 19. The adapter asclaimed in claim 18 wherein said main body portion and said tapered bodyportion are formed of plastic and connected together at a joint, one ofsaid main body portion and said tapered body portion including a firstlip that projects radially outwardly and the other of said main bodyportion and said tapered body portion including a second lip thatprojects radially inwardly, said first and second lips being sized suchthat they can bypass each other with slight interference to permit oneof said lips to bypass the other said lip to form an inseparable snapfit joint between the main body portion and the tapered body portion.20. A method of ultrasonically sensing liquid level in a samplecontainer comprising, a) forming an adapter with a mouth opening and atapered body portion that extends below the mouth opening, the mouthopening being sized to hold an open-mouthed sample container, b) forminga main body portion of the adapter to extend below the tapered bodyportion with a main body diameter that is larger than the mouth openingof the adapter to permit accommodation of the adapter in a sample tuberack, c) placing the sample container in the mouth opening of theadapter such that a lip flange of the sample container rests on themouth opening of the adapter, d) placing the adapter with the samplecontainer in a sample tube rack such that the elevation of the lipflange of the sample container in the adapter is at a known height froma reference level, e) providing an ultrasound detector at apredetermined elevation above the lip flange of the sample containerwhen the adapter and sample container are supported in the sample tuberack, f) directing a first ultrasonic wave from the ultrasound detectorat the sample container and identifying a first ultrasonic echo from thesample container lip flange based on a known distance between theultrasound detector and the lip flange of the sample container, g)directing a second ultrasonic wave from the ultrasound detector atliquid level in the sample container and identifying a second ultrasonicecho as corresponding to the liquid level in the sample container basedon known characteristics of the first ultrasonic echo and on adifference between the second ultrasonic echo and the first ultrasonicecho because there is a greater distance between the ultrasound detectorand the liquid level than between the ultrasound detector and the lipflange of the sample container, and h) allowing the tapered surface ofthe adapter to deflect any ultrasonic echoes from the tapered surfaceaway from the ultrasonic detector, whereby the adapter permits echoreflection back to the ultrasonic detector of only the first and secondultrasonic waves.